Endodontic training blocks and tooth models are typically used for practicing endodontic treatments or for the development and evaluation of endodontic instruments for root canal treatment, in both cases as an alternative to the use of extracted teeth or cadaver teeth.
A typical root canal endodontic treatment starts by creating a suitable opening into the pulp chamber to allow access to the root canals in the floor of the pulp chamber. Secondly, the root canals are cleaned out with dedicated instruments (“files”) which remove ailing pulp and dentin tissues and ream the root canals into a conical shape with a smooth and clean surface. After irrigation with a disinfection media, the root canals are sealed and obturated with a filling material.
This type of treatment holds several risks such as incomplete cleaning of the root canal, typically at the apical part of the canals; fracture of the root canal instruments (e.g. files) during reaming of the root canal or an incomplete filling of the root canal. Due to the complexity of this procedure, it is important that adequate root canal treatment simulation systems are available in order to allow dental trainees to practice on lifelike cases and/or to validate new root canal instruments on lifelike cases.
Currently existing tooth models have limitations with respect to mimicking lifelike cases, U.S. Pat. No. 3,947,967 refers to root canal models comprising a transparent plastic body with a cavity mimicking the pulp chamber and the root canal(s). The transparent body has at least one flat side in order to have an undistorted view of the root canal. U.S. Pat. No. 4,137,633 refers to a variation of above-mentioned root canal model providing a resilient mass at the apical part of the root canal cavity in order to simulate the tactile feedback when reaching the apical point of the root canal with an endodontic file. U.S. Pat. No. 5,503,562 refers to an improvement of the former root canal model, by configuring at least one side wall of the transparent body to optically magnify the root canal. This in order to augment the visual inspection of the cavity and the results of root canal treatments performed on the cavity. The above mentioned types of endodontic training blocks have limitations when it comes to representing the lifelike situation. First of all these blocks do not have a tooth like external shape, and therefore inherently do not allow for a realistic simulation of a root canal treatment, which starts with creating an opening in the occlusal surface of the tooth to access the pulp chamber and subsequently the root canal(s). Secondly, these endodontic training blocks are typically made by moulding or milling techniques making it virtually impossible to duplicate the complex shape of natural root canals, which is often a network of canals having irregular shapes and directions, including among others furcations, accessory (lateral) canals, or even partially calcified root canals.
Patent JP5241498 refers to an endodontic tooth model for treatment simulation, consisting of a dentinal part enclosing at least the pulp chamber and a cavity—optionally filled with a softer material—representing the pulp chamber and the root canal(s). US Patent US2009/0263774 A1 refers to an artificial tooth that simulates the anatomical features of natural teeth, such as the appearance and internal anatomy, and the physical properties, such as bone-like hardness, density and radio-opacity to provide for anatomically correct contrast during x-ray imaging. The two latter inventions do allow for simulating the complete root canal treatment, starting with the creation of the access cavity to the pulp chamber. However, the degree at which the complex shape of natural root canals can be mimicked is poor due to the conventional production method i.e. moulding. Complex clinical cases (C shaped canals, lateral root canals, fractured teeth, etc.) can therefore not be produced, while being highly relevant for the training of dental professionals and the evaluation of new instruments.
Another drawback of the existing endodontic treatment simulation systems such as commercially available tooth models is the fact that there is no easy way to compare the performed treatment with an optimized treatment. This feedback would be very beneficial to the dental trainee in order to improve his/her endodontic treatment techniques. Patent application WO 2007/108030 A1 refers to an endodontic training device that comprises an enclosing housing for a tooth and allows for x-ray imaging.
As such, multiple radiographs can be taken from the tooth, prior, during or after the root canal treatment in order to rapidly evaluate the treatment sequence. This device does not allow the comparison with a predetermined ideal root canal preparation in 3D. In contrast, the dental trainee can only incrementally monitor the progress of the root canal treatment in one or more planar views, but is not provided with the ability to assess to what extent the realized preparation conforms to a desired or acceptable preparation in three dimensions.
Patent DE4100636 (A1) describes the manufacturing of a root-shaped dental implant by copy milling from an impression formed in the root area of an extracted natural tooth or in the artificial tooth socket of a taken impression.
In the prior art (“Dental Root Implants Produced by the Combined Selective Laser Sintering/Melting of Titanium Powders”, N K Tolochko, V V Savich, L Froyen, G Onofrio, E Signorelli and V I Titov, Proc Instn Mech Engrs, Part L: J Materials: Design and Applications, Vol 216, No 4, 2002, pp 267-270) the manufacturing of dental root implants that almost correspond to natural dental roots in their geometrical, structural and mechanical characteristics by a combined process of selective laser sintering (SLS) and selective laser melting (SLM) of Titanium powders is described. Using these methods (SLS and SLM), it is possible to manufacture implants with a graded structure, i.e. a relatively high porosity at the surface and a high density in the core. However these root shaped implants do not have an internal, structure mimicking the pulp chamber and the root canal(s).